1. Field of the Invention
The present invention generally relates to a radio frequency identification (RF-ID) system and method capable of confirming data detected by a sensor in addition to basic data necessary for certification.
2. Description of the Related Art
With the development of radio technologies as a substitute for existing bar-code technology, a variety of RF-ID systems have been proposed. The systems have been used in a variety of manners, e.g., prepayment of a bus fare or a parking permit and permitting access to a restricted area, such as a laboratory. The basic configuration of these RF-ID systems includes a tag, having an integrated circuit (IC) and an antenna, and a reader. The antenna of the tag outputs information from the IC about the tagged object in the form of the radio frequency signal and the reader receives and confirms the information.
RF-ID systems are classified primarily as an active type or a passive type, depending on how power is supplied to the IC installed in the tag. In the active type system, power is supplied to the IC from a battery included in the tag. In the passive type system, power is supplied to the IC by an inductive current in response to a magnetic wave transmitted from the reader. The passive type system allows a thin, lightweight card to be used as the tag. The tag for the passive type system includes a coil, which induces current via a received magnetic wave and which serves as the antenna transmitting data output from the IC.
FIG. 1A is schematic diagram of a structure of a general passive type RF-ID system. As shown therein, the system includes a tag 10 having a coil 30 and an IC 20, an external antenna 40 and a reader 50. FIG. 1B is block diagram explaining the operation of the RF-ID system.
With reference to FIGS. 1A and 1B, when the card reader 50 approaches the tag 10, the coil 30 in the tag 10 receives a magnetic wave radiated by the external antenna 40 (S110). The coil 30 generates an inductive current from the magnetic wave according to Faraday's law (S120).
When the voltage generated due to the inductive current drives the IC 20, the IC 20 accesses data stored in an internal memory (not shown) (S130). Such data may include the tag owner's name, member number, resident registration number, whether or not entrance and exit is acceptable, manufacturing date and manufacturer of the tagged product, or any other useful information. The coil 30 serves as an internal antenna for the tag 10 and outputs the data in radio frequency signal format (S140).
The RF-ID reader 50 receives the data through the external antenna 40 (S150) and demodulates the received data (S160). Thus, the tag information can be confirmed (S170).
In such an existing RF-ID or other identification system, it may be desirable to also transmit additional, real-time data. Such real-time data can be obtained by measuring the present status of the tagged object or an environment of the tagged object. For example, in the case of barcodes, which are currently most widely used with industrial products, only the basic information on manufacturing number and price of that product is output. However, when storing sensitive goods, such as wine, it is necessary to keep the goods under certain conditions, e.g., within a certain temperature range, in order to efficiently manage the goods.
In order to measure a present status, the certification system must include a sensor. In case of a RF-ID system, the tag should include a sensor in addition to the coil and the IC. The most logical approach would involve designing the IC to convert the information from the sensor into digital data, so that additional data is output along with the basic data. This can be implemented with recently developed SOC (System On Chip) technology.
However, in addition to requiring a new IC design, if the RF-ID system is implemented by adding the sensor in this manner, other practical problems arise. First, since an analog-to-digital (A/D) converter is required for converting the sensor information into digital data, the increased power consumption due to the A/D converter excludes use of the passive type tag. Second, using a more complicated IC will inevitably increase the cost per tag. This increased cost would prevent widespread use of such a system.